Diethylene glycol bis(allyl carbonate) has hitherto been used widely as a resin for plastic lenses. While this resin is advantageous because of its excellent impact resistance and transparency and satisfactory light scattering characteristics, it has a low refractive index of 1.50, requiring some thickness for obtaining refraction equal to that of glass.
It is known, on the other hand, that various diacrylates or dimethacrylates are easily radical-polymerized to provide lenses having high transparency. For example, resins obtained from di(meth)acrylates having a bromine-containing bisphenol A skeleton (refer to JP-A-59-184210, the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-59-193915), di(meth)acrylates having a sulfur-containing aromatic skeleton (refer to JP-A-60-26010 and JP-A-62-195357), etc. are known to exhibit such excellent optical characteristics as having a high refractive index and a high Abbe's number at balance.
In general, cured resins comprising a highly crosslinked structure obtained by polymerization of di(meth)acrylate compounds are excellent in heat resistance, abrasion resistance, and transparency, but, in turn, tend to have brittleness. In order to overcome brittleness, use of urethane (meth)acrylated bromine-containing bisphenol A derivatives have been proposed as disclosed in JP-A-60-51706. However, these resins have not only an increased specific viscosity due to the bromine atom and also deteriorated weather resistance.
JP-A-2-141702 discloses resins having improved impact resistance which are obtained by copolymerizing bis(meth)acryloxymethyl-tricyclodecane and a polyfunctional thiol, e.g., pentaerythritol tetrakis(.beta.-thiopropionate). Though having a high Abbe's number, these resins have a relatively low refractive index of 1.55 or less. Further, JP-A-63-309509 proposes to use a polymerizable monomer obtained by reacting a thiol and divinylbenzene. In this case, however, the radical terminal should be treated with pyrogallol.